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* [PATCH net] net/bpfilter: initialize pos in __bpfilter_process_sockopt
@ 2020-07-30 16:09 Christoph Hellwig
  2020-07-30 16:13 ` Christian Brauner
  0 siblings, 1 reply; 6+ messages in thread
From: Christoph Hellwig @ 2020-07-30 16:09 UTC (permalink / raw)
  To: davem, kuba, ast, daniel; +Cc: netdev, bpf, Christian Brauner, Rodrigo Madera

__bpfilter_process_sockopt never initialized the pos variable passed to
the pipe write.  This has been mostly harmless in the past as pipes
ignore the offset, but the switch to kernel_write no verified the
position, which can lead to a failure depending on the exact stack
initialization patter.  Initialize the variable to zero to make
rw_verify_area happy.

Fixes: 6955a76fbcd5 ("bpfilter: switch to kernel_write")
Reported-by: Christian Brauner <christian.brauner@ubuntu.com>
Reported-by: Rodrigo Madera <rodrigo.madera@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Rodrigo Madera <rodrigo.madera@gmail.com>
---
 net/bpfilter/bpfilter_kern.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 1905e01c3aa9a7..4494ea6056cdb8 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -39,7 +39,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
 {
 	struct mbox_request req;
 	struct mbox_reply reply;
-	loff_t pos;
+	loff_t pos = 0;
 	ssize_t n;
 	int ret = -EFAULT;
 
-- 
2.27.0


^ permalink raw reply	[flat|nested] 6+ messages in thread

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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-07-30 16:09 [PATCH net] net/bpfilter: initialize pos in __bpfilter_process_sockopt Christoph Hellwig
2020-07-30 16:13 ` Christian Brauner
2020-07-31  0:07   ` Daniel Borkmann
2020-08-01 19:48     ` Alexei Starovoitov
2020-08-03 14:56       ` Daniel Borkmann
2020-08-03 15:36         ` Rodrigo Madera

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